The invention relates to a method for assembling an endoscope with a first tubular channel for receiving image-transmitting components, and with a second channel for receiving light guides.
The invention likewise relates to such an endoscope.
Endoscopes have become widely used in the medical sector and have opened up the possibility of what is referred to as minimally invasive surgery. In the meantime, a further area of use has been in the field of so-called “industrial endoscopy” in which the endoscopes are used for visual inspection of hollow spaces, for example in engines, vehicle bodyworks, aircraft turbines, buildings, etc.
Such endoscopes have a first tubular channel for receiving image-transmitting elements. These image-transmitting elements are elements of an optical system, such as lenses, in particular rod lenses, spacers, diaphragms, prisms, filters or the like. These transmit the image in the direction from distal to proximal. In electronic image-processing, a miniature camera in the form of a CCD chip is used which converts the optical signals into electrical signals.
The light needed for viewing purposes is provided by light guides which conduct the light from a light source in the proximal to distal direction. These light guides are usually formed by a bundle of glass fibers.
When assembling the endoscope, the light guides are introduced in the form of a bundle of glass fibers directly into a second channel, and the latter is then closed at both ends. This second channel is formed by a second tube being pushed over the first tubular channel and then surrounding the latter so that a gap between the first tubular channel and the second tube forms the second channel as a channel having the cross section of a continuous ring or with a crescent-shaped and if appropriate non-continuous cross section. Such endoscopes have an elongate shaft in which the two channels for receiving the image-transmitting and light-conducting components are provided. At the proximal end, the shaft opens into an endoscope housing whose proximal end, depending on its design, in turn has an eyepiece cup or an attachment for a camera module. By virtue of the flexibility of the thin light guides made of glass fibers, it is possible to route these to a light guide attachment protruding transversely with respect to the longitudinal axis of the shaft. In a fully assembled endoscope, a first elongate portion of the light guide extends along the shaft axis in the second channel and is then angled to the side at about 90° in the housing via a corresponding bend or curve in the direction of the light guide attachment.
The shaft of such an endoscope is usually composed of an outer tube in which an inner tube is received in whose interior the first channel is formed and which serves to receive the image-transmitting elements. If the inner tube is arranged coaxially with respect to the outer tube, a hollow cylindrical space is formed between the outside face of the inner tube and the inside face of the outer tube, and this space forms the second channel for receiving the light guides in the shaft area.
If the inner tube is arranged laterally offset in the outer tube, in most cases such that it bears along an outer surface line on an inner surface line of the inside face of the outer tube, then a crescent-shaped space is obtained which represents the second channel for receiving the light guides.
It has been found that assembly of the light guide in the form of a loose bundle of glass fibers requires a certain amount of practice and considerable dexterity. However, it is difficult to avoid some of the glass fibers breaking during assembly, in which case they cannot be used to conduct light. It has also been found that, after a large number of sterilization cycles, moisture or other forms of contamination can penetrate into the second channel and adversely affect the quality of light conduction.
The glass fiber bundle is fixed at the distal and proximal ends by adhesive bonding. Creep of the adhesive along the glass fibers and away from the fixing locations has been noted, which leads to undesired adhesion of individual glass fibers to one another and undesired adhesion of glass fibers to the inner or outer tube away from the fixing locations at the ends. In the event of thermal and mechanical expansion stresses and shocks, this leads to fracturing of glass fibers, and these can then no longer serve for light conduction.
It is an object of the present invention is to remedy this situation and make available a method and an endoscope of the type mentioned at the outset which is easy to assemble and which ensures lasting and excellent light conduction.